1. Field of the Invention
The invention relates to a plasma display panel (PDP) of a self light emitting type using the gaseous discharge.
2. Description of Related Art
In recent years, a plasma display panel of an area discharge AC driving type is expected to be put into practical use as a large and thin color display apparatus.
FIG. 1 is a partial schematic diagram showing the structure of a plasma display panel of the area discharge AC driving type. The structure of the plasma display panel of the area discharge AC driving type will now be described below.
In FIG. 1, a plurality of pairs of row electrodes X and Y are arranged on a glass substrate 1 to be placed on a display side, so as to be parallel with each other. The row electrodes are constituted by transparent electrodes made of a transparent conductive film and metal electrodes made of a metal film each of which are laminated on an edge portion on an opposite side of a discharge gap of a transparent conductive film in order to augment the the conductivity of the transparent conductive film. Furthermore, a dielectric layer 2 is formed so as to cover the row electrodes X and Y. A protective layer (not shown) made of MgO is formed on the dielectric layer 2.
A plurality of column electrodes 4 which are arranged at predetermined intervals are formed on the inner surface side of a glass substrate 3 on the rear side so as to be in parallel with each other. Fluorescent layers 5 covering the column electrodes 4 are formed.
The row electrodes X and Y and the column electrodes 4 are arranged so as to be perpendicular to each other while maintaining a distance between them, thereby forming discharge spaces 6 between the glass substrate 1 on the display surface side and the glass substrate 3 on the rear side. A rare gas is hermetically charged and filled in the discharge spaces 6.
A rib (partition) 7 of a predetermined height is formed between the respective column electrodes 4 on the glass substrate 3 on the rear side. The ribs 7 partition the plural pairs of row electrodes X and Y and the plural column electrodes 4 which cross each other, thereby each forming a unit light emitting region having a light emitting surface of a predetermined area.
For the charging of the rare gas, at first, a frit paste containing amorphous or crystalline glass powder of a low melting point as a main component is coated onto an outer peripheral non-display region of the glass substrate 3 on the rear side so as to surround a display region. Then a temporary baking is performed, and sealing layers 8 are formed. After that, the glass substrate 3 on the rear side is turned upside down, the glass substrate 1 on the display surface side and the glass substrate 3 on the rear side are overlaid, and a periphery is temporarily fixed with clips.
An evacuation and gas charging hole 9 is formed in the glass substrate 3 on the rear side. A chip tube 11 is attached to the evacuation and gas charging hole 9 by an adhesive agent 10 made of a frit paste containing amorphous glass powder of a low melting point as a main component.
The chip tube 11 is attached as mentioned above, the temporarily fixed two glass substrates 1 and 3 are put into a chamber (not shown) and heated, the sealing layers 8 and adhesive agent 10 are baked, the two glass substrates 1 and 3 are adhered, and the chip tube 11 is hermetically bonded into the evacuation and gas charging hole 9 of the glass substrate 3.
A vacuum pump and a gas cylinder are connected to the chip tube 11 through a closable valve (not shown). The closable valve of the vacuum pump is first opened and the inner air is vacuumed by the vacuum pump, thereby evacuating the air in the space between the two glass substrates 1 and 3. In this instance, the two glass substrates 1 and 3 are heated at a predetermined temperature during the evacuation.
Subsequently, the closable valve of the gas cylinder is opened and the rare gas is introduced from the gas cylinder. After the gas has been introduced in this manner, the opening portion of the chip tube 11 is closed and the rare gas is introduced into a space between the two glass substrates 1 and 3.
Although the chip tube was sealed and bonded by using the amorphous glass powder of a low melting point as mentioned above, the amorphous glass has a temperature difference of tens of degree between a working temperature for seal bonding (temperature at which the glass is softened and fluidity increases) and a solidifying temperature (temperature at which the glass is not softened and does not flow).
Now considering performance such as color temperature characteristics or the like of the plasma display panel, it is better that the working temperature to seal bond the chip tube is low. On the contrary, it is better that the heating temperature in the evacuating step is high. When the amorphous glass powder of a low melting point is used to seal bond the chip tube as mentioned above, if the heating temperature in the evacuating step is raised, the fluidity of the amorphous glass increases and the glass is likely to leak, so that there is a drawback that reliability of high vacuum sealing can be insufficient.